Local enforcement of accuracy in fabricated models

ABSTRACT

The systems and methods disclosed herein employ a combination of digital three-dimensional modeling and rapid fabrication technologies to provide pre-indexed, pre-registered, and/or precut components for articulated dental models. Dental articulators and components of dental models as described herein use a positioning key to encode positional information for components of the dental model, and/or a reference grid on mounting surfaces to enforce local accuracy of fabricated parts against a fixed reference array.

RELATED APPLICATIONS

This application is a divisional of U.S. Ser. No. 11/467,866, filed Aug.28, 2006, now allowed, which claims the benefit of U.S. ProvisionalApplication No. 60/761,078, filed Jan. 20, 2006, the disclosure of whichis incorporated by reference in their entirety herein.

BACKGROUND

The invention relates to dentistry, and more particularly to fabricationof dental objects and articulators.

Conventional dentistry employs physical casts of human dentition as afoundation for a variety of fabrication techniques. The impressionmaterials used in this process, such as polymerizing silicone andpolyether, theoretically capture an accurate dental impression. However,the initial impression may be flawed, and even a perfect impression maydegrade over time as a result of thermal fluctuations, inherentplasticity, and rough handling. While the materials used to obtaindental impressions and create subsequent dental models have improved,the basic process steps remain prone to human error.

Sometimes, errors become so severe that the desired end product, such asa crown, cannot be manufactured. In other cases, the process introducesjust enough error that the resulting prosthetic simply will not fit intoa target space within a dental patient's dentition. This latterdifficulty may place significant burdens on the craftsmanship of thepracticing dentist to work the prosthetic and/or tooth surface into asuitable shape, or cause increased delay and costs if a new impressionis required.

As another disadvantage, the process of taking the impression may causesignificant discomfort to a patient, who must retain the impressionmaterial in the mouth while an impression is curing.

Recent advances in three dimensional imaging technology have introducedthe possibility of a handheld, three-dimensional scanner that can besuitably adapted to acquisition of highly accurate, detailed surfacedata directly from within a dental patient's mouth—a virtual digitaldental impression—that, once captured accurately, will not degrade, andcan be easily reviewed, analyzed, and/or transmitted to remotemanufacturing facilities. While this technology introduces thepossibility of significant advances in digital dentistry, there remainsa need for improved dental processes and models that employ virtualdigital dental impressions to reduce manual labor and opportunities forerror inherent in conventional dentistry.

SUMMARY

The systems and methods disclosed herein employ a combination of digitalthree-dimensional modeling and rapid fabrication technologies to providepre-indexed, pre-registered, and/or precut components for articulateddental models. Dental articulators and components of dental models asdescribed herein use a positioning key to encode positional informationfor components of the dental model, and/or a reference grid on mountingsurfaces to enforce local accuracy of fabricated parts against a fixedreference array.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention and the following detailed description of certainembodiments thereof may be understood by reference to the followingfigures.

FIG. 1 shows a dental image capture system.

FIG. 2 is a block diagram of a generalized manufacturing process fordental objects.

FIG. 3 shows a milling machine.

FIG. 4 shows a stereo lithography apparatus.

FIG. 5 shows a three-dimensional printer.

FIG. 6 is a high-level flow chart of a dental object fabricationprocess.

FIG. 7 illustrates a number of dental objects that can be fabricatedfrom a three-dimensional representation of dentition.

FIGS. 8A-8C show a number of dental objects that can be fabricated froma three-dimensional representation of dentition.

FIG. 9 shows a dental object that can be fabricated from athree-dimensional representation of dentition.

FIG. 10 shows a dental object that can be fabricated from athree-dimensional representation of dentition.

FIG. 11 is a top view of a digital representation of a digital dentalmodel.

FIG. 12 shows a restoration that can be fabricated from athree-dimensional representation of dentition.

FIG. 13 shows a dental articulator.

FIG. 14 shows a digital dental model with two partial arches inocclusion.

FIG. 15 depicts a cross section of an alignment geometry including apositioning key.

FIG. 16 shows a virtual application of an articulator geometry to adental model.

FIG. 17 shows a dental model including alignment geometry.

FIG. 18 shows pieces of a dental model fabricated from a digital dentalmodel.

FIG. 19 shows a dental model assembled on an articulator.

FIG. 20 shows a dental articulator.

DETAILED DESCRIPTION

Described herein are systems and methods of fabricating dental objectsfor use in dental articulators based upon three-dimensional digital datacaptured from an intraoral scan. While the description emphasizescertain scanning technologies and certain combinations of fabricationtechniques, it will be understood that additional variations,adaptations, and combinations of the methods and systems below will beapparent to one of ordinary skill in the art, such as fabrication ofdental restorations not specifically described, or use ofthree-dimensional output or fabrication technologies not specificallyidentified herein, and all such variations, adaptations, andcombinations are intended to fall within the scope of this disclosure.Further, while the techniques described herein are particularly usefulfor mechanical alignment of pieces of an articulating dental model, andmanufacturing and design of same, it will be understood that thetechniques described herein may be more generally applied to anyenvironment where it is desired to capture the alignment and relativemotion of a number of separately manufactured rigid bodies.

In the following description, the term “image” generally refers to atwo-dimensional set of pixels forming a two-dimensional view of asubject within an image plane. The term “image set” generally refers toa set of related two dimensional images that might be resolved intothree-dimensional data. The term “point cloud” generally refers to athree-dimensional set of points forming a three-dimensional view of thesubject reconstructed from a number of two-dimensional views. In athree-dimensional image capture system, a number of such point cloudsmay also be registered and combined into an aggregate point cloudconstructed from images captured by a moving camera. Thus it will beunderstood that pixels generally refer to two-dimensional data andpoints generally refer to three-dimensional data, unless another meaningis specifically indicated or clear from the context.

The terms “three-dimensional surface representation”, “digital surfacerepresentation”, “three-dimensional surface map”, and the like, as usedherein, are intended to refer to any three-dimensional surface map of anobject, such as a point cloud of surface data, a set of two-dimensionalpolygons, or any other data representing all or some of the surface ofan object, as might be obtained through the capture and/or processing ofthree-dimensional scan data, unless a different meaning is explicitlyprovided or otherwise clear from the context.

A “three-dimensional representation” may include any of thethree-dimensional surface representations described above, as well asvolumetric and other representations, unless a different meaning isexplicitly provided or otherwise clear from the context.

In general, the terms “render” or “rendering” refer to a two-dimensionalvisualization of a three-dimensional object, such as for display on amonitor. However, it will be understood that three-dimensional renderingtechnologies exist, and may be usefully employed with the systems andmethods disclosed herein. As such, rendering should be interpretedbroadly unless a narrower meaning is explicitly provided or otherwiseclear from the context.

The term “dental object”, as used herein, is intended to refer broadlyto subject matter specific to dentistry. This may include intraoralstructures such as dentition, and more typically human dentition, suchas individual teeth, quadrants, full arches, pairs of arches which maybe separate or in occlusion of various types, soft tissue, and the like,as well bones and any other supporting or surrounding structures. Asused herein, the term “intraoral structures” refers to both naturalstructures within a mouth as described above and artificial structuressuch as any of the dental objects described below that might be presentin the mouth. Dental objects may include “restorations”, which may begenerally understood to include components that restore the structure orfunction of existing dentition, such as crowns, bridges, veneers,inlays, onlays, amalgams, composites, and various substructures such ascopings and the like, as well as temporary restorations for use while apermanent restoration is being fabricated. Dental objects may alsoinclude a “prosthesis” that replaces dentition with removable orpermanent structures, such as dentures, partial dentures, implants,retained dentures, and the like. Dental objects may also include“appliances” used to correct, align, or otherwise temporarily orpermanently adjust dentition, such as removable orthodontic appliances,surgical stents, bruxism appliances, snore guards, indirect bracketplacement appliances, and the like. Dental objects may also include“hardware” affixed to dentition for an extended period, such as implantfixtures, implant abutments, orthodontic brackets, and other orthodonticcomponents. Dental objects may also include “interim components” ofdental manufacture such as dental models (full and/or partial), wax-ups,investment molds, and the like, as well as trays, bases, dies, and othercomponents employed in the fabrication of restorations, prostheses, andthe like. Dental objects may also be categorized as natural dentalobjects such as the teeth, bone, and other intraoral structuresdescribed above or as artificial dental objects such as therestorations, prostheses, appliances, hardware, and interim componentsof dental manufacture as described above.

Terms such as “digital dental model”, “digital dental impression” andthe like, are intended to refer to three-dimensional representations ofdental objects that may be used in various aspects of acquisition,analysis, prescription, and manufacture, unless a different meaning isotherwise provided or clear from the context. Terms such as “dentalmodel” or “dental impression” are intended to refer to a physical model,such as a cast, printed, or otherwise fabricated physical instance of adental object. Unless specified, the term “model”, when used alone, mayrefer to either or both of a physical model and a digital model.

FIG. 1 shows an image capture system. In general, the system 100 mayinclude a scanner 102 that captures images from a surface 106 of asubject 104, such as a dental patient, and forwards the images to acomputer 108, which may include a display 110 and one or more user inputdevices such as a mouse 112 or a keyboard 114. The scanner 102 may alsoinclude an input or output device 116 such as a control input (e.g.,button, touchpad, thumbwheel, etc.) or a display (e.g., LCD or LEDdisplay) to provide status information.

The scanner 102 may include any camera or camera system suitable forcapturing images from which a three-dimensional point cloud may berecovered. For example, the scanner 102 may employ a multi-aperturesystem as disclosed, for example, in U.S. Pat. Pub. No. 20040155975 toHart et al., the entire contents of which is incorporated herein byreference. While Hart discloses one multi-aperture system, it will beappreciated that any multi-aperture system suitable for reconstructing athree-dimensional point cloud from a number of two-dimensional imagesmay similarly be employed. In one multi-aperture embodiment, the scanner102 may include a plurality of apertures including a center aperturepositioned along a center optical axis of a lens and any associatedimaging hardware. The scanner 102 may also, or instead, include astereoscopic, triscopic or other multi-camera or other configuration inwhich a number of cameras or optical paths are maintained in fixedrelation to one another to obtain two-dimensional images of an objectfrom a number of slightly different perspectives. The scanner 102 mayinclude suitable processing for deriving a three-dimensional point cloudfrom an image set or a number of image sets, or each two-dimensionalimage set may be transmitted to an external processor such as containedin the computer 108 described below. In other embodiments, the scanner102 may employ structured light, laser scanning, direct ranging, or anyother technology suitable for acquiring three-dimensional data, ortwo-dimensional data that can be resolved into three-dimensional data.

In one embodiment, the scanner 102 is a handheld, freely positionableprobe having at least one user input device 116, such as a button,lever, dial, thumb wheel, switch, or the like, for user control of theimage capture system 100 such as starting and stopping scans. In anembodiment, the scanner 102 may be shaped and sized for dental scanning.More particularly, the scanner may be shaped and sized for intraoralscanning and data capture, such as by insertion into a mouth of animaging subject and passing over an intraoral surface 106 at a suitabledistance to acquire surface data from teeth, gums, and so forth. Thescanner 102 may, through such a continuous acquisition process, capturea point cloud of surface data having sufficient spatial resolution andaccuracy to prepare dental objects such as prosthetics, hardware,appliances, and the like therefrom, either directly or through a varietyof intermediate processing steps. In other embodiments, surface data maybe acquired from a dental model such as a dental prosthetic, to ensureproper fitting using a previous scan of corresponding dentition, such asa tooth surface prepared for the prosthetic.

Although not shown in FIG. 1, it will be appreciated that a number ofsupplemental lighting systems may be usefully employed during imagecapture. For example, environmental illumination may be enhanced withone or more spotlights illuminating the subject 104 to speed imageacquisition and improve depth of field (or spatial resolution depth).The scanner 102 may also, or instead, include a strobe, flash, or otherlight source to supplement illumination of the subject 104 during imageacquisition.

The subject 104 may be any object, collection of objects, portion of anobject, or other subject matter. More particularly with respect to thedental fabrication techniques discussed herein, the object 104 mayinclude human dentition captured intraorally from a dental patient'smouth. A scan may capture a three-dimensional representation of some orall of the dentition according to particular purpose of the scan. Thusthe scan may capture a digital model of a tooth, a quadrant of teeth, ora full collection of teeth including two opposing arches, as well assoft tissue or any other relevant intraoral structures. In otherembodiments where, for example, a completed fabrication is beingvirtually test fit to a surface preparation, the scan may include adental prosthesis such as an inlay, a crown, or any other dentalprosthesis, dental hardware, dental appliance, or the like. The subject104 may also, or instead, include a dental model, such as a plastercast, wax-up, impression, or negative impression of a tooth, teeth, softtissue, or some combination of these.

The computer 108 may be, for example, a personal computer or otherprocessing device. In one embodiment, the computer 108 includes apersonal computer with a dual 2.8 GHz Opteron central processing unit, 2gigabytes of random access memory, a TYAN Thunder K8WE motherboard, anda 250 gigabyte, 10,000 rpm hard drive. This system may be operated tocapture approximately 1,500 points per image set in real time using thetechniques described herein, and store an aggregated point cloud of overone million points. As used herein, the term “real time” means generallywith no observable latency between processing and display. In avideo-based scanning system, real time more specifically refers toprocessing within the time between frames of video data, which may varyaccording to specific video technologies between about fifteen framesper second and about thirty frames per second. More generally,processing capabilities of the computer 108 may vary according to thesize of the subject 104, the speed of image acquisition, and the desiredspatial resolution of three-dimensional points. The computer 108 mayalso include peripheral devices such as a keyboard 114, display 110, andmouse 112 for user interaction with the camera system 100. The display110 may be a touch screen display capable of receiving user inputthrough direct, physical interaction with the display 110.

Communications between the computer 108 and the scanner 102 may use anysuitable communications link including, for example, a wired connectionor a wireless connection based upon, for example, IEEE 802.11 (alsoknown as wireless Ethernet), BlueTooth, or any other suitable wirelessstandard using, e.g., a radio frequency, infrared, or other wirelesscommunication medium. In medical imaging or other sensitiveapplications, wireless image transmission from the scanner 102 to thecomputer 108 may be secured. The computer 108 may generate controlsignals to the scanner 102 which, in addition to image acquisitioncommands, may include conventional camera controls such as focus orzoom.

In an example of general operation of a three-dimensional image capturesystem 100, the scanner 102 may acquire two-dimensional image sets at avideo rate while the scanner 102 is passed over a surface of thesubject. The two-dimensional image sets may be forwarded to the computer108 for derivation of three-dimensional point clouds. Thethree-dimensional data for each newly acquired two-dimensional image setmay be derived and fitted or “stitched” to existing three-dimensionaldata using a number of different techniques. Such a system employscamera motion estimation to avoid the need for independent tracking ofthe position of the scanner 102. One useful example of such a techniqueis described in commonly-owned U.S. application Ser. No. 11/270,135,filed on Nov. 9, 2005, the entire contents of which is incorporatedherein by reference. However, it will be appreciated that this exampleis not limiting, and that the principles described herein may be appliedto a wide range of three-dimensional image capture systems.

The display 110 may include any display suitable for video or other raterendering at a level of detail corresponding to the acquired data.Suitable displays include cathode ray tube displays, liquid crystaldisplays, light emitting diode displays and the like. In someembodiments, the display may include a touch screen interface using, forexample capacitive, resistive, or surface acoustic wave (also referredto as dispersive signal) touch screen technologies, or any othersuitable technology for sensing physical interaction with the display110.

FIG. 2 is a conceptual block diagram of participants in a generalizedmanufacturing process for dental objects. The system 200 may begin witha patient 202 being scanned by a scanner 204, such as the scanner 102and image capture system 100 described above, to obtain a digitalsurface representation 206 of one or more intraoral structures. This mayinclude scans before and/or after a surface has been prepared to receivea dental restoration or other dental object. So, for example, apre-preparation scan may be taken to capture a shape of the originalanatomy and any occlusion information useful in creating a restoration,and a prepared surface scan may be taken to use as a basis for creatingthe restoration, and in particular for shaping the restoration to theprepared surface. Articulation data relating to the orientation and/orrelative motion of an upper and lower arch may also be obtained throughone or more scans of the arches in occlusion, or through othertechniques such as still images or video of the arches in variousorientations, or various dimensional measurements captured directly fromthe arches, or a physical bite registration captured on a thin sheet ofmaterial.

In one embodiment, a second scanner such as a PMD[vision] camera fromPMD Technologies, may be employed to capture real-time,three-dimensional data on dynamic articulation and occlusion. While thisscanner employs different imaging technology (time-of-flight detectionfrom an array of LEDs) than described above, and produces results withresolution generally unsuitable for reconstruction of dental models,such a scanner may be employed to infer motion of, e.g., opposing dentalarches with sufficient resolution to select an axis for articulation orotherwise capture dynamic information that can be applied to two or morerigid bodies of a dental object scan. This data may be supplemented withmore precise alignment data statically captured from digital or manualbite registration to provide reference or calibration points forcontinuous, dynamic motion data.

The digital surface representation 206 may be processed with one or morepost-processing steps 208. This may include a variety of dataenhancement processes, quality control processes, visual inspection, andso forth. Post-processing steps may be performed at a remotepost-processing center or other computer facility capable ofpost-processing the imaging file, which may be, for example a dentallaboratory. In some cases, this post-processing may be performed by theimage capture system 100 itself. Post-processing may involve any numberof clean-up steps, including the filling of holes, removing of outliers,etc.

Data enhancement may include, for example, smoothing, truncation,extrapolation, interpolation, and any other suitable processes forimproving the quality of the digital surface representation 206 orimproving its suitability for an intended purpose. In addition, spatialresolution may be enhanced using various post-processing techniques.Other enhancements may include modifications to the data, such asforming the digital surface representation 206 into a closed surface byvirtually providing a base for each arch, or otherwise preparing thedigital surface representation for subsequent fabrication steps.

In a quality control process, the digital surface representation 206 maybe analyzed for the presence of holes or regions of incomplete orinadequate scan data. The digital surface representation 206 may also beautomatically examined for unexpected curvature or asymmetry to ascanned arch, or other apparent defects in the acquired data. Otherquality control processes may incorporate additional data. For example,a current scan may be compared to previous scans for the same patient.As another example, a selection of a dental restoration may be analyzedalong with a scan of a tooth surface prepared for the restoration inorder to evaluate the suitability of the surface preparation and anysurrounding dentition for receiving the restoration. More generally, anyprocess for evaluating data in the digital surface representation 206with respect to its quality, internal consistency, or intended use, maybe used in a post-processing quality control process.

The digital surface representation 206 may also be displayed for humaninspection, such as by providing a perspective rendering of a pointcloud of acquired surface data on a display.

Following any manual or automated post-processing, the resulting digitalmodel may be transmitted to a rapid fabrication facility 216, asindicated by an arrow 209. In addition, articulation data 218 in anysuitable form may be transmitted for use in subsequent processing steps,as well as a prescription or other specification for manufacture of arestoration, appliance, hardware, and the like. The rapid fabricationfacility 216 may be a dental laboratory, an in-house dental laboratoryat a dentist's office, or any other facility with machinery to fabricatephysical models from digital models. The rapid fabrication facility 216may, for example, include a milling system 210, a stereo lithographysystem 212, Digital Light Processing (not shown), or a three-dimensionalprinter 214, or some combination of these. The milling system 210 mayinclude, for example, a CNC milling machine. Milling systems may be usedto take a block of material and create a variety of outputs, includingfull-arch models, dies, wax-ups, investment chambers or a finalrestoration or appliance. Such blocks may include ceramic-based,particle-board, wax, metals or a variety of other materials. Dentalmilling systems such as Procera from Nobel Biocare Inc. or Cerec fromSirona Inc. may also be used to create a final dental hardwarecomponent. The stereo lithography system 212 may include, for example, aViper System by 3D Systems, Inc. The three-dimensional printer 214 mayinclude, for example, an InVision HR printer from 3D Systems. Each ofthese fabrication techniques will be described in greater detail below.Other techniques for three-dimensional manufacturing are known, such asFused Deposition Modeling, Laminated Object Manufacturing, SelectiveLaser Sintering, and Ballistic Particle Manufacturing, and may besuitably be adapted to use in certain dental applications describedherein. More generally, three-dimensional fabrication techniquescontinue to become available. All such techniques may be adapted to usewith the systems and methods described herein, provided they offersuitable fabrication resolution in suitable materials for use with thevarious dental objects described herein.

The rapid fabrication facility 216 may use the articulation data 218 andthe digital model to generate one or more dental objects, such as one ormore full arch models 220, one or more dies 222, one or more waxups 224,one or more investment chambers 226, and/or one or more finalrestorations or appliances 228. Some components, such as the dies 222and arches 220, may be inserted into an articulated model 234 such as anarticulator with a standard base 230 or a custom base 232. Articulatorsand articulated models are described in greater detail below. A dentallaboratory may employ these various components to complete a restoration236, which may be returned to a dentist for placement into/onto thedentition of the dental patient.

Various aspects of this system and process will now be described ingreater detail, beginning with the rapid fabrication techniques that maybe employed with the systems and methods described herein.

FIG. 3 shows a milling machine that may be used with the systems andmethods herein. In particular, FIG. 3 illustrates a ComputerizedNumerically Controlled (“CNC”) milling machine 300 including a table302, an arm 304, and a cutting tool 306 that cooperate to mill undercomputer control within a working envelope 308. In operation, aworkpiece (not shown) may be attached to the table 302. The table 302may move within a horizontal plane and the arm 304 may move on avertical axis to collectively provide x-axis, y-axis, and z-axispositioning of the cutting tool 306 relative to a workpiece within theworking envelope 308. The cutting tool 306 may thus be maneuvered to cuta computer-specified shape from the workpiece.

Milling is generally a subtractive technology in that material issubtracted from a block rather than added. Thus pre-cut workpiecesapproximating commonly milled shapes may advantageously be employed toreduce the amount of material that must be removed during a milling job,which may reduce material costs and/or save time in a milling process.More specifically in a dental context, it may be advantageous to begin amilling process with a precut piece, such as a generic coping, ratherthan a square block. A number of sizes and shapes (e.g., molar, incisor,etc.) of preformed workpieces may be provided so that an optimal piecemay be selected to begin any milling job. Various milling systems havedifferent degrees of freedom, referred to as axes. Typically, the moreaxes available (such as 4-axis milling), the more accurate the resultingparts. High-speed milling systems are commercially available, and canprovide high throughputs.

In addition a milling system may use a variety of cutting tools, and themilling system may include an automated tool changing capability to cuta single part with a variety of cutting tools. In milling a dentalmodel, accuracy may be adjusted for different parts of the model. Forexample, the tops of teeth, or occlusal surfaces, may be cut morequickly and roughly with a ball mill and the prepared tooth and dentalmargin may be milled with a tool resulting in greater detail andaccuracy. In general, milling systems offer the advantage of workingdirectly with a finished material so that the final product is free fromcuring-related distortions or other artifacts. As a disadvantage, a highprecision requires smaller cutting tools and correspondingly slowerfabrication times.

CNC milling and other milling technologies can be employed formanufacturing dental models, dental model components, wax-ups,investment chambers, and other dental objects, some of which aredescribed in greater detail below. In addition specialty dental millingequipment exists, such as the Cerac system from Sirona Dental. Anotheruseful milling system for the dental fabrication processes describedherein is a copy milling system that permits manual or automatedtransfer of a three-dimensional form from a physical object to a milledtarget.

All such milling systems as may be adapted to use in the dentalapplications described herein are intended to fall within the scope ofthe term “milling system” as used herein, and a milling process mayemploy any of the milling systems described herein.

FIG. 4 shows a stereo lithography apparatus (“SLA”) that may be usedwith the systems and methods described herein. In general, the SLA 400may include a laser 402, optics 404, a steering lens 406, an elevator408, a platform 410, and a straight edge 412, within a vat 412 filledwith a polymer. In operation, the laser 402 is steered across a surfaceof the polymer to cure a cross-section of the polymer, typically aphotocurable liquid resin, after which the elevator 408 slightly lowersthe platform 408 and another cross section is cured. The straight edge412 may sweep the surface of the cured polymer between layers to smoothand normalize the surface prior to addition of a new layer. In otherembodiments, the vat 412 may be slowly filled with liquid resin while anobject is drawn, layer by layer, onto the top surface of the polymer.One useful commercial embodiment of an SLA is the SCS-1000HD availablefrom Sony Corporation.

Stereo lithography is well-suited for the high volume production ofdental models and dies, because parts may be batched on machines forrapid production. When optimized, these parts may be used in lieu ofplaster dental models and other dental objects. An SLA may be usefullyemployed for fabrication of dental models, arches and cast-able parts,as well as for other high-accuracy and/or high-throughput applications.In some embodiments an SLA may receive a digital surface representationdirectly from a clinician's intraoral scan, and manufacture a dentalmodel corresponding to the patient's dentition with or withoutsurrounding soft tissue. Where groups of related objects aremanufactured, they may be physically interconnected during the SLAprocess so that a complete set or kit is readily handled afterfabrication. Individual pieces of the kit may be separated and trimmedor finished as appropriate, such as by a qualified technician in adental laboratory. In such embodiments, dental objects may be orientedso that the interconnecting frame or other mechanical infrastructureonly contacts objects on non-critical surfaces. Thus, for example,connections might be avoided on opposing surfaces of a dental arch wherefine detail is to be preserved.

An SLA may require significant optimization of operating parameters suchas draw speeds, beam diameters, materials, etc. These parameters may bestored in a “style” file, which may also vary accuracy and speed indifferent areas of a model. So, for example, a tooth within an arch thatcontains a surface prepared for a dental prosthetic may be optimized fordetail/accuracy, while a distant tooth on a different arch may beoptimized for speed.

A related technology, Digital Light Processing (“DLP”), also employs acontainer of curable polymer. However, in a DLP system, atwo-dimensional cross section is projected onto the curable material tocure an entire transverse plane at one time. DLP fabrication currentlyprovides resolution on the order of 40 microns, with further sub-pixelaccuracy available using a number of techniques.

FIG. 5 shows a three-dimensional printer. The three-dimensional printer500 may include a print head 502, a material supply 504, a platform 506,and positioning mechanisms (not shown) such as elevators, arms, belts,and the like that may be used to position the print head 502 relative toa printed item 508 during a printing operation. In operation, the printhead 502 may deposit curable photopolymers or powders in alayer-by-layer fashion.

Various types of three-dimensional printers exist. Some printers deposita polymer in conjunction with a support material or a bonding agent. Insome systems, the stage may move as well to control x-y motion of theprint head 502 relative to the platform 506 and printed item 508. Modelsprinted on such systems may require finishing steps, such as removal ofwax supports and other cleaning processes. Three-dimensional printersare well suited to rapid fabrication of small parts such as wax patternsor wax-ups, as well as dies and other relatively small dental objects.One commercial system suitable for three-dimensional dental printingapplications is the InVision HR printer from 3D Systems.

Three-dimensional printing may be usefully employed for fabricating avariety of dental objects including wax-ups that may be cast by a dentallaboratory to create a traditional metal substructure restoration, oftenreferred to as a Porcelain-Fused-to-Metal (“PFM”) restoration. Directthree-dimensional printing of the wax-up (much of the shape of which maybe directly inferred from a digital surface representation of apatient's dentition) may omit intermediate processing steps inconventional dentistry, where the shape of the dentition travels from animpression to a model to a wax-up. This approach advantageously preventsloss or corruption of data between the source (the patient's dentition)and the target wax-up by transitioning directly from an intraoral scanto a waxup, bypassing intermediate processing steps. Other usefulapplications of three-dimensional printing are described below ingreater detail.

It will be appreciated that other rapid prototyping systems are known inthe art. Thus, the terms fabricate, fabricating, and fabrication, asused herein, will be understood to refer to the fabrication technologiesabove, as well as any other rapid prototyping or other manufacturingtechnology that might be adapted to manufacture of custom dentalobjects, including, without limitation, selective laser sintering(“SLS”), fused deposition modeling (“FDM”), laminated objectmanufacturing (“LOM”), and so forth, unless a different meaning isexplicitly provided or otherwise clear from the context. Similarly, anyof the above technologies, either alone or in combination, may operateas a means for fabricating, printing, manufacturing, or otherwisecreating the dental objects described herein. It will be appreciatedthat the fabrication steps described above with reference to particulartechnologies may be followed by additional steps such as curing,cleaning, and so forth to provide a final product.

The manufacturing techniques described above may be combined in variousways to provide a multimodal fabrication process. Thus, for example, aCNC milling machine may be used to create a die for a tooth requiringgreater detail than an SLA can provide, while the SLA may be employedfor a model of a dental arch that contains the die. This multimodalapproach may deploy the advantages of various technologies in differentaspects of the fabrication process, such as using stereo lithography forspeed, milling for accuracy, and three-dimensional printing forhigh-speed fabrication of small parts. In addition, as described in oneof the examples below, other mass production techniques such asinjection molding may be employed for certain standardized parts, suchas an articulator.

FIG. 6 is a high-level flow chart of a dental object fabricationprocess. This process 600 employs a three-dimensional representation ofdentition acquired directly from an intraoral scan, and advantageouslybypasses a number of processing steps used in conventional dentistry.

In general the process 600 may begin with data acquisition, as shown instep 602. Data acquisition may include any acquisition of a digitalsurface representation, or other three-dimensional or otherrepresentation of dentition suitable for use in a dental objectfabrication process. The data acquisition may be performed using, forexample, the scanner 102 and image capture system described above withreference to FIG. 1. In certain embodiments, a number of different scansmay be acquired, such as scans to establish articulation and occlusionof arches, or scans before and after a surface preparation, which may beused jointly to create a prosthetic or the like. For example, toestablish articulation and occlusion of arches, scans may be made of theupper and lower arches, and a bite scan may be taken with the upper andlower arches in various types of occlusion and so forth. Used jointly,these scans may provide full detail for an upper and lower arch, alongwith static and dynamic data concerning the alignment and motion of thearches.

Once suitable data has been acquired, one or more modeling operationsmay be performed, as shown in step 604. This may include modeling stepssuch as ditching a virtual die of a digital dental model, specifying atooth for treatment, filling holes or otherwise correcting data, biteregistration, and/or fully designing a restoration, prosthetic, hardwareor other dental object(s), as well as any other modeling or digitalmodel manipulation useful in a dental context. Modeling may be performedusing commercially available Computer Automated Design (“CAD”) or otherthree-dimensional modeling tools, or special-purpose dental modelingsoftware such as the in Lab CAD/CAM system from Sirona.

For example, modeling may include bounding the surface representation toform a solid, and then creating a void space, or collection of voidspaces within the solid that do not affect dentally significant surfacessuch as the dentition or surrounding soft tissue. This mayadvantageously result in significant reductions in material required tofabricate a dental model from the voided digital model, thus reducingmaterial costs as well as time to manufacture dental models.

Modeling for articulated models may include using scan data togetherwith bite registration and other data to position two rigid bodiescorresponding to opposing arches in a relative orientation correspondingto the position of the arches in a dental patient's mouth. Once soaligned, the arches may be mechanically registered to a common referencesurface that corresponds to, e.g., the top and bottom of a dentalarticulator. This process is described in greater detail below.

As another example, modeling may include the computer aided design of anitem of removable dental hardware. This may account for the shape ofteeth and soft tissue, jaw position, occlusal and/or articulatingrelationships, soft palette and any other spatial or dynamiccharacteristics of a patient's mouth, as well as any objectives for thehardware. For example, a bruxism night guard may simply serve toseparate opposing arches slightly, and may be designed to permit orprohibit breathing through the mouth. A suitable device may be virtuallydesigned that fits the teeth, provides a small amount of interveningmaterial, and conforms to any other aspects of the patient's mouth suchas the tongue, lips, and the like. As another example, a snore nightguard may be virtually designed to displace one arch slightly in amanner that provides greater clearance for the palette. Other items ofremovable hardware, such as a surgical guide, removable denture, orstent may similarly be virtually designed within a digital modelingenvironment. Once a design has been established, the resulting digitalmodel may be fabricated using any of the fabrication techniquesdescribed below. A number of other modeling steps are described withreference to specific fabrication processes below. It will beappreciated that the term “modeling” as used herein may refer to anyprocessing of a digital dental model including fully automated,semi-automated, and/or manual processes such as those noted throughoutthis description.

As shown in step 606, a prescription may be prepared. This specifies atype of restoration, prosthetic, or the like, and may include a varietyof additional information related to a manufacturer, color, finish, diespacing, and so forth. It will be appreciated that the prescription step606 may be performed before the modeling step 608, such as in a processwhere a dentist transmits the initial digital surface representationfrom a patient to a dental laboratory along with a prescription, leavingsome or all of the modeling to the dental laboratory.

As shown in step 608, one or more dental objects may be fabricated.Fabrication may be performed using any of the fabrication technologiesdescribed above, either alone or in various combinations, using datafrom one of the modeling systems described above, which may bereformatted or otherwise adapted as necessary for a particular printing,milling, or other fabrication technology. Also, as will be clear fromsome of the examples below, fabrication may include a combination ofdifferent fabrication technologies. For example, dental model may bethree-dimensionally printed with a space for a die, and the die may bemilled of a different material for use in subsequent processing steps.Thus, the term “fabrication” as used herein is intended to refer to anysuitable fabrication technology unless a specific fabrication technologyis explicitly identified, or otherwise clear from the context. A numberof specific fabrication examples are discussed below in greater detail.

As shown in step 610, a prosthetic or other dental object may bereturned to a dentist for placement into a patient's dentition.

It will be appreciated that the above processes may be realized inhardware, software, or any combination of these suitable for the dataacquisition and fabrication technologies described herein. This includesrealization in one or more microprocessors, microcontrollers, embeddedmicrocontrollers, programmable digital signal processors or otherprogrammable devices, along with internal and/or external memory. Themay also, or instead, include one or more application specificintegrated circuits, programmable gate arrays, programmable array logiccomponents, or any other device or devices that may be configured toprocess electronic signals. It will further be appreciated that arealization may include computer executable code created using astructured programming language such as C, an object orientedprogramming language such as C++, or any other high-level or low-levelprogramming language (including assembly languages, hardware descriptionlanguages, and database programming languages and technologies) that maybe stored, compiled or interpreted to run on one of the above devices,as well as heterogeneous combinations of processors, processorarchitectures, or combinations of different hardware and software. Atthe same time, processing may be distributed across devices such as acamera and/or computer and/or fabrication facility in a number of waysor all of the functionality may be integrated into a dedicated,standalone device. All such permutations and combinations are intendedto fall within the scope of the present disclosure.

It will also be appreciated that means for performing the stepsassociated with the processes described above may include any suitablecomponents of the image capture system 100 described above withreference to FIG. 1, as well as any components of the fabricationfacilities described with reference to FIGS. 3-5, along with anysoftware and/or hardware suitable for controlling operation of same. Allsuch realizations and means for performing the processes disclosedherein are intended to fall within the scope of this disclosure.

FIG. 7 illustrates a number of dental objects that can be fabricatedfrom a three-dimensional representation of dentition. A full arch model700 may include an upper arch 702, a lower arch 704, a die 706 with aprepare surface 708 and a ditched region 710, and an articulator 712that maintains the upper arch 702 and the lower arch 704 in a desiredocclusal relationship. It will be appreciated that, while FIG. 7 depictsa single die 706 in the upper arch 702, a dental model 700 may includeany number of dies 706, some or all of which may be in the lower arch704.

Generally, the die 706 is manually cut from a dental model by a dentaltechnician for preparation of a restoration or the like from theprepared surface 708 thereof. However, applying the principles describedherein, the die may be virtually cut during the modeling step above, andseparately fabricated using any of the techniques above. Thus in oneembodiment, a technique for fabricating pre-cut dental models isdisclosed. As a significant advantage, this approach removes a manualprocessing step from conventional dentistry. While the arches 702, 704may, in general be fabricated using a process selected for high speed orlow cost, the die may be fabricated using a process selected forhardness, or more generally, for suitability for subsequent processingsteps. Thus in one embodiment the arches 702, 704 of the model may befabricating using three-dimensional printing or DLP and the precut die706 may be fabricated using computerized milling. The die 706 may also,or instead, be pre-indexed using, e.g., a pair of posts on the die 706and matching holes on the upper arch 702, so that, although manufacturedseparately, the die 706 may be mechanically registered to the upper arch702.

In conventional dental fabrication, a die spacer (not shown) such as athin painted film is often used to provide spacing between a modelsurface preparation and a dental component such as a crown or otherrestoration. The spacing may accommodate cement used to attach the finalrestoration to the actual surface preparation in a patient's mouth. Thespacing may also account for dimensional changes that occur to variousmaterials during drying, curing, or other handling during variousfabrication steps and may provide a margin of error for a finalrestoration. In one aspect, a restoration may be virtually modeleddirectly from a digital surface representation of dentition before andafter a surface preparation, which may advantageously remove the needfor manually applied die spacers. In some embodiments where control ofdie spacer thickness is desired, or various types of intermediatephysical modeling are anticipated, a die spacer may be virtually createdand integrated into a model. The die spacer may be integrated directlyinto a printed component such as a die to account for any physicaldisplacement or offset that the die spacer would have provided. Inaddition to virtual integration of dies spacers for a cementation voidsor dimensional variation, the modeling step may include the addition ofa layer of occlusal relief to provide similar accommodation for occlusalspacing between a restoration and a prepared surface (and by extension,between the restoration and a tooth of an opposing arch).

In various processes, it may be faster and/or cheaper to fabricatecomponents of a dental model in a hollow form, that is, omitting anymaterial not required for creating a prosthetic or fitting theprosthetic within occlusal surfaces of the arches 702, 704. Thus,portions of the upper arch 702, the lower arch 704, and/or the die 706may be hollowed during the modeling step(s) in preparation forfabrication. Other modeling steps may usefully be performed. Forexample, it is common practice to “ditch” the die(s) of a dental modelfor increased physical exposure of the surface preparation, and inparticular, the margin, for subsequent inspection, manipulation, andprocessing. This may be performed virtually such as through a modelingtool that permits automatic, semi-automatic, or manual ditching of a diein a digital surface representation or other digital model of dentition.In general, the degree of automation will depend on the ability toeither automatically detect or provide by way of electronic annotation,a demarcation of the margin line for a surface preparation below whichthe die may be ditched.

Modeling may provide additional useful features to the dental model 700.For example, if articulation and/or occlusion data is provided with thedigital version of the dental model, attachment interfaces 716 such asslots, holes, notches, alignment guides, or the like, may automaticallyadded during the modeling step that properly orient the arches 702, 704in the articulator 712 (provided, of course, the type or dimensions ofthe articulator are known). The mechanical interface between thearticulator 712 and the arches 702, 704 may include screws, interlockingtongue and groove regions, or other mechanical components to removablyattach the arches 702, 704 to the articulator. Where a commercialarticulator 712 also includes positioning adjustments, the output of themodeling step(s) may also specify one or more settings for theseadjustments, which may be included along with a digital dental model, ordirectly physically marked onto the model for reproduction duringfabrication. In another useful technique for aligning the arches 702,704 one or more outside edges of the upper arch 702 model and the lowerarch 704 model may be beveled so that, when placed on a flat surfacealong that edge, the teeth of the arches 702, 704 remain in theiroccluded orientation. This may be accomplished by, for example,virtually placing the arches 702, 704 in occlusion within a modelingenvironment, and then defining a plane within the environment thatcrosses both arches 702, 704. As illustrated in FIG. 7, a rear edgewhere the articulator 712 attaches to the model 700 defines such aplane, however one or more additional areas of the edge may be similarlymodified, such as the side edges, the front edge, or intermediateregions of the edge of the model 700.

More generally, the fabrication technologies described above may be usedin combination with a variety of digital modeling tools to directlyfabricate dental objects such as restorations, prosthetics, appliances,and hardware, as well as a variety of interim components of dentalmanufacture used to create any of the foregoing. A more detaileddescription of techniques for fabricating articulated dental models isprovided below with reference to FIG. 12 et seq.

FIG. 8 shows a number of dental objects that can be fabricated from athree-dimensional representation of dentition. In particular, FIG. 8Ashows a tray 800 for a dental model and FIG. 8B shows a base 850 for adental model, and FIG. 8C shows a pre-articulated arch 870 for use withthe tray 800 of FIG. 8A.

The tray 800 of FIG. 8A may include a mass 802 with a receptacle 804such as a groove or indentation and one or more mechanical registrationfeatures 806, such as ridges, grooves, slots, or any other physicalfeatures that might be used to receive a base (FIG. 8B) into the tray800 in a predetermined orientation. The mass 802 may be shaped and sizedfor use with an articulator. In certain embodiments, the mass 802 may beshaped and sized for a particular commercially available articulator.The receptacle 804 and the mechanical registration features 806 may becustom designed for a particular dental model, or they may bestandardized so that any base 850 (FIG. 8B) may be modeled with a matingform to the standardized tray 800. In such embodiments, the tray 800 maybe mass produced using a process such as injection molding, or any othersuitable high volume, low cost manufacturing process. The tray 800 maybe mass produced in a number of sizes, such as small, medium, and large,to accommodate various rough sizes of dentition, or the tray 800 may bemass produced in a number of sizes adapted for specific commerciallyavailable articulators, or the tray 800 may be mass produced in a singlesize. Thus, the tray 800 may be created from a three-dimensional digitalmodel of dentition in the modeling step(s) described above, or the tray800 may be mass produced.

It will be appreciated that, while the physical registration features806 of the tray 800 may be adapted to receive a base (FIG. 8) for anentire arch of dentition, the physical registration features 806 mayalso, or instead, be used to orient a single die (not shown), or anumber of dies within a dental model such as an articulated dentalmodel. In one embodiment, an entire arch may be precut and preindexedwithin a virtual environment in the modeling step(s) described above,using varying degrees of automation. Thus, while FIG. 8B shows a unitarybase 850 for a dental model, the base 850 may actually consist of one ormore precut, preindexed dies, and/or a unitary base for any remainingdentition from a digital model.

The base 850 of FIG. 8B may be created from a three-dimensional digitalmodel of dentition in the modeling step(s) described above. The base 850may include one or more physical registration features 852 such asridges, grooves, slots, or any other physical features that might beused to fit the base to the tray into the tray 800 in a predeterminedorientation. The base 850 may also include one or more keys 854 forreceiving individual teeth or groups of teeth in a dental model. Eachkey 854 may have a unique shape and or size so that each tooth or groupof teeth in the dental model is uniquely indexed to a location on thebase 850. While the keys 854 are depicted as cylindrical posts, it willbe appreciated that any mechanical registration scheme may be employedto provide a unique location on the base 850 for each tooth or group ofteeth in a dental model, including pairs of pins, grooves, slots,varying shapes or impressions, and so forth.

The base 870 of FIG. 8C may be created from a three-dimensional digitalmodel of dentition in the modeling step(s) described above. The base 870may, in general function resemble the base 850 of FIG. 8B, and may beprecut, pre-indexed, and/or pre-articulated as described herein, exceptthat the base 870 of FIG. 8C includes a surface model of dentitionregistered to the tray 800, rather than indexed sites for individualteeth of the model as with the base 850 of FIG. 8B.

Although not depicted in FIG. 8, it will be understood that individualteeth or groups of teeth may also be created in a modeling step suchthat they mate to the keys 854 of the base in a unique arrangement.Varying degrees of automation may be provided for such modeling steps inwhich, for example, a computerized process fully automates the locationof natural teeth and/or surface preparations within the digital model ofdentition, or a human identifies some teeth or portions of teeth toassist a computerized process, or a fully manual process in which ahuman operator places a base 850 and keys within a volumetricrepresentation of dentition. Thus for example, a dental model may bevirtually created and directly fabricated that includes a base 850 withholes preprinted for one or more corresponding pins on one or more dies,which may also be directly fabricated from the digital dental model withpreprinted, matching pins. In this example, the dental model may bedirectly printed from the digital model as a plurality of preindexedcomponents ready for assembly at a dental laboratory.

In addition, as noted above, the model may be prearticulated so that thefabricated dental model assembles on an articulator into a model thatarticulates in a manner corresponding to articulation of the sourcedentition. This may include various aspects of static articulation suchas occlusal contact points and arch positions in various types ofocclusion, as well as dynamic occlusion such as (where available fromthe digital model or supporting data) lateral excursions, jaw motion,and the like.

In one embodiment, the base 850 may be used to orient a dental modelwithin an articulator. Articulated models are used by a dentallaboratory technician to determine how to contour the anatomy of a crownor other prosthetic so as to maintain, or in some cases, improve thebite of a patient. By pre-articulating the models during a modeling andfabrication process, a laboratory may save considerable time and effort.In the traditional process, labs are forced to prepare plaster dentalarch models from physical impressions taken by a dentist, and manuallymount dental arch models into a face bow, a hinged apparatus thatsimulates the jaw of the patient. The alignment is then manuallyperformed on the mounted models with reference to articulation paper—waxpaper on which the patient bites—received from a dentist.

Using information concerning a particular articulator, such as apredetermined commercially available articulator, a particular tray 800,such as a mass-produced tray shaped for use with the articulator, and athree-dimensional representation of dentition that includes articulationand/or occlusion information, the base 850 may readily be adapted toorient teeth within the articulated dental model in their naturalocclusion and/or with their natural articulation. In general, this maybe achieved by positioning the arches of the digital model in occlusionand locating a hinge or pivot point for an articulator relative to thedigital model. The base 850 may then be adapted to bridge any spacebetween a virtual model of the mass-produced tray, as oriented relativeto the hinge of the articulator, and the teeth of the digital model ofdentition. When the resulting base 850 and any teeth or groups of teethare fabricated, the articulated model can be assembled using theregistration features discussed above to obtain a properly articulateddental model, that is, a model with articulation and/or occlusioncorresponding to the source of the digital dental model such as a dentalpatient.

It will be understood that, while a full arch model is depicted in FIG.8, the tray 800 and base 850 may be for a quadrant, or one or more teethof a quadrant, along with one or more opposing teeth, for use in anarticulator that does not require a full arch.

Leveraging rapid fabrication technologies such as milling, stereolithography, and digital light processing allows for the virtualcreation and direct fabrication of the individual components of aprecut, preindexed, and/or prearticulated dental model. Thus in oneembodiment, disclosed herein is a method and system for fabricating adental model including a plurality of components. While this may includethe components of a dental model described above, it may also, orinstead, include other components such as investment molds, waxups, andso forth, which may be modeled with varying degrees of automation andtransmitted to a dental laboratory or rapid manufacturer as a virtualmodel of a kit of cooperating dental components. Some or all of thecomponents of the kit may then be directly fabricated from the virtualmodel, which may be fabricated with an interconnecting wireframe orother structure to maintain components of the kit in a connectedrelationship until finishing and assembly by a dental technician.Additional examples of these general techniques are provided below.

FIG. 9 shows a dental object that can be fabricated from athree-dimensional representation of dentition. More particularly, awaxup 900 of a typical single tooth dental die is shown. Waxups may beemployed in a lost wax fabrication process to form restorations or aninvestment casting chamber or other interim components of dentalmanufacture. For example, the waxup may instead be employed to create apressable mold for use with a press-to-zirconium restoration, a press-toalumina restoration, or a pressable ceramic restoration. Waxups may becosmetic or diagnostic models used first to test a restoration (or otherdental object) design, and then to physically fabricate the finalrestoration in a lost wax process. In a conventional dental fabricationprocess, a waxup is formed by placing wax directly on a dentalmodel—applied to a surface prepared for a restoration—and hand-craftinga desired restoration. Using the techniques described herein, a waxupmay be fabricated directly from a digital three-dimensionalrepresentation. For example, the form of the waxup may be inferredthrough a direct spatial comparison of a scan of dentition before apreparation to a scan of the dentition after a surface has been preparedfor a dental object. Where the prosthetic is cosmetic, rather thansimply restorative, a tooth may be automatically, semi-automatically, ormanually designed, with the waxup inferred from a spatial comparison ofthe design to the prepared surface. The digital model of the waxup maythen be fabricated using any of the techniques described above.

In addition to capturing the correct form for a waxup, a modeling stepfor a waxup may include the addition of one or more sprues that providepaths into (for investment material) and/or out of (for venting) aninvestment chamber used with the waxup. Thus, one or more sprues may beadded to the waxup and directly fabricated using any of the techniquesdescribed herein. While a waxup of a single die is depicted in FIG. 9,it will be appreciated that a number of variations, such as a waxup fora restoration bridging two or more teeth, are also intended to fallwithin the meaning of the term waxup as used herein.

FIG. 10 shows a dental object that can be fabricated from athree-dimensional representation of dentition. More specifically, FIG.10 illustrates an investment casting chamber 1000 for a single unitpressed or metal restoration. Investment chambers are used in a lost waxprocess to create metal or ceramic-pressed copings or finalrestorations. The investment chamber 1000 includes a first mold 1002 anda second mold 1004 which, when placed together, enclose a space defininga restoration geometry. The molds 1002, 1004 may also include a path1008 for investment. In a conventional dental fabrication procedure, theinvestment casting chamber 1000 is physically formed from a model suchas the waxup described above. However, applying the principles describedherein, the investment chamber 1000 may be virtually created from adigital three-dimensional representation of dentition and directlyfabricated using the techniques described above. In one embodiment, acomputerized milling machine may be employed to fabricate an investmentchamber from a suitable material for investment or pressing.

It will be understood that, while the waxups and investment chambersdescribed above may be used to fabricate full restorations such ascrowns in their entirety, they may also, or instead, be employed tofabricate a coping or other substructure for use in aPorcelain-Fused-to-Metal (“PFM”) restoration, or any other technique inwhich the final restoration is fabricated in a number of steps thatinclude creation of a substructure.

Thus there is disclosed herein a method of fabricating casting modelsfrom three-dimensional surface data captured during an intraoral scan ofa dental patient's mouth. While any number of suitable virtual modelingsteps may be performed to obtain a digital version of the casting model,the entire process may advantageously be performed without resort tointermediate physical modeling. The casting model may include theinvestment chamber described above or other investment molds or pressedceramic molds, as well as an investment cast for an investment mold suchas a model of a full restoration, a coping, or a full anatomical form ofone or more teeth.

While not depicted in FIG. 10, it will be understood that other moldsmay be fabricated using the techniques described herein. For example, abruxism or snoring night guard may be fabricated from a soft plastic orrubber. The guard may be virtually designed during the modeling step(s)described above, and a corresponding mold may be virtually created basedupon the digital design for the guard. The mold may then be fabricatedfrom any suitable material using the techniques described herein, andthe mold may be filled with a pourable, curable polymer or othersubstance that will dry or cure into the night guard. Still moregenerally, any dental object suitable for fabrication in a casting ormolding process may advantageously be fabricated using a mold, cast, orother similar device created directly from a digital model ofcorresponding human dentition.

FIG. 11 is a top view of a digital representation of a digital dentalmodel. The digital dental model 1100 may include a three-dimensionaldigital surface representation of a plurality of teeth 1102 in a dentalarch, such as used for a dental cast or other dental object. The digitaldental model 1100 may also include a number of features added during amodeling step as described above.

For example, the digital dental model 1100 may include one or morebeveled edges 1104, as described above in reference to FIG. 7. Theseedges 1104 may serve to align, e.g., top and bottom arches of a fulldental model in an occluded relationship when the two pieces of themodel are placed on a flat surface. This feature may aid in handling andworking with a physical realization of the full dental model. The edges1104 may be added to an initial digital representation of scan data froman intraoral scan of dentition, and reproduced in a dental modelfabricated from the digital model using any of the techniques describedabove.

As another example, the digital dental model 1100 may include one ormore markings 1106. While depicted as printed text, it will beunderstood that a variety of markings may be added to the digital dentalmodel 1100 including coloring or text created with pigment, embossmentor other three-dimensional surface markings, bar codes, graphics, and soforth. The marking may perform a number of functions such as specifyinga physical arrangement of model components or specifying a location of acomponent within a model, identifying a source or intended destinationof the digital dental model 1100, identifying a stock keeping unit(“sku”) or other inventory number of a component, or highlighting aregion of dental significance. For example, the markings 1106 mayidentify features such as a restoration margin, a soft tissue boundary,an alignment or occlusion point for a pair of arches, an undercut areafor design of a removable prosthetic framework, an orthodontic bracketposition or positioning guide, and the like. The markings 1106 includean identification aid concerning the model such as a marking thatidentifies a patient, a dentist, or a dental laboratory. The marking1106 may include a logo, such as of a dental laboratory, a bar code, astock keeping unit code, or any other code that uniquely identifies themodel or associates the model with a category of models. The markings1106 may provide conceptual guides such as a fiducial or a calibrationlandmark. The markings 1106 may also include a void space to receive,e.g., an RFID tag or other tracking device that may be used to manage aninventory of dental models.

The markings 1106 may, as a specific example, show a margin as a highlycontrasted line around a prepared tooth surface. As another example, theprepared surface may itself be marked in a different color from the restof the model for easy visual identification. These and other markingsmay be added to a digital dental model 1100, which may be fabricatedusing any of the techniques described above to provide a marked dentalmodel.

The digital dental model 1100 may also include soft tissue 1108 such asgums, palate, and so forth. In some embodiments, the soft tissue 1108may be independently modeled and fabricated. This may entail a degree ofestimation concerning the shape of teeth below the gumline, which may besupplemented by one or more direct measurements or scans of sub-gumlinedentition or models of characteristic tooth shapes. The soft tissue 1108may be fabricated using any of the techniques described above, and inparticular, fabrication techniques that can yield a pliable fabricatedmodel adapted for removal and reattachment to a corresponding model ofthe hard dentition. The physical soft tissue model may be fabricatedfrom a material that includes a property of live soft tissue such ascolor, texture, or consistency, or from a material that can be cured tohave such properties. The physical soft tissue model may usefully serveto simulate planned soft tissue contour after healing, or to provide atemplate or surgical guide to aid a clinician during a surgicalprocedure.

FIG. 12 shows a restoration that can be fabricated from athree-dimensional representation of dentition. It will be understoodthat, while a multi-tooth bridge is depicted, the restoration 1200 maybe any indirect restoration or appliance—as distinguished from directrestorations such as amalgams that are created directly within a dentalpatient's mouth—suitable for manufacture using the techniques describedherein. Thus the restoration 1200 may include an array of componentsthat restore the structure and/or function of existing dentition, suchas crowns, bridges, veneers, inlays, onlays, composites, temporaryrestorations, and various substructures such as copings and the like.Other dental objects such as dentures, partial dentures, implants,retained dentures and so forth may also be directly fabricated from asuitably manipulated model of human dentition and/or any surfacepreparations of the dentition for the restoration(s).

The modeling step(s) may include inferring a model from a comparison ofpre-preparation and post-preparation scans of a restoration site. Wherecosmetic or clinically indicated enhancements or other alterations areindicated, the modeling step(s) may also, or instead, included thevirtual creation of a target three-dimensional form for one or moreteeth according to aesthetic or other dental principles. The creation ofa target form may be automated, semi-automated, or manual, although atleast some degree of automation is likely to be used for creation of afull three-dimensional structure. In addition, the modeling step(s) mayinclude adapting the target form to any surrounding dentition includingopposing and adjacent teeth. A model for the restoration 1200 (or otherdental object as described above) may then be inferred from a comparisonof surface preparation (if any) obtained from a scan of a dentalpatient's mouth to the target form for the restoration 1200.

Fabrication may include any of the fabrication techniques describedabove. For example, the restoration 1200 may be fabricated usingcomputerized milling of a pre-formed ceramic blank, such as a zirconiaceramic having a nano-crystalline porous structure. The resultingproduct may then be sintered into a hard ceramic structure. Sinteringmay cause some shrinkage—uniform in all dimensions for suitable startingmaterials—and the milled product may be modeled with a correspondinglylarger size in order for the final product to sinter to suitabledimensions for the restoration site. A veneer may then be applied toachieve a restoration that resembles natural human dentition. As above,the model may be sized to account for a thickness of veneer applied tothe milled and sintered product.

As another example, fabrication may include three-dimensional printingor fabricating with a stereo lithography apparatus. The fabrication maybe performed with a material that inherently possesses, or cures topossess, or can otherwise be processed to possess one or morecharacteristics of human dentition, such as color, hardness, strength,wear resistance, texture, and biocompatibility. For example, thematerial may include a sinterable metal and/or ceramic, or anappropriate resin or other polymer, along with any additives suitablefor printing or stereo lithography processes. Suitable materials areknown in the three-dimensional printing and stereo lithography arts. Inone embodiment, a biocompatible veneer may be applied to the fabricatedmodel.

In one embodiment, a temporary restoration may be three-dimensionallyprinted into a printed model of any suitable material, and the printedmodel may be used with a copy milling machine—i.e., a milling machinefor transferring a physical form from one material such as the printedmodel to another material such as a ceramic or other material suitablefor a temporary restoration. The digital source for the printed modelmay, at the same time or any other convenient time for the dentist, betransmitted to a remote facility such as a rapid manufacturer or adental laboratory for manufacture of a permanent restoration. Thetemporary restoration may be replaced with the permanent restoration ata subsequent dental visit by a dental patient.

An application of the foregoing techniques and technologies is nowdescribed in greater detail with respect to a dental articulator with analignment grid.

FIG. 13 illustrates an articulator 1300 that may be used with objectsfabricated from a three-dimensional representation of dentition. Thearticulator includes a first arm 1302 and a second arm 1322 each havinga mounting surface end 1306, 1326 and an opposing pivot end 1304, 1324respectively. The second arm 1322 and the first arm 1302 may slidablyand detachably engage at their respective pivot ends 1304, 1324 througha lateral motion as indicated by an arrow 1350. The arms 1302, 1322 may,once so engaged, pivot on a pin, an axle, bearings, or other structuresuitable for rotational engagement of the arms 1302, 1322. In thedepicted embodiment, the arms engage and pivot through an interlockingpin 1352 on the second arm 1322 which is received into a circularretainer 1354 on the first arm 1302. Opposite of their pivot end, eacharm 1302, 1324 may have a mounting surface 1308, 1328 to receive one ormore dental objects that have a corresponding geometry in apredetermined orientation and position.

While a simple rotational engagement is one convenient technique formoveably attaching the arms 1302, 1322 to one another, it will beunderstood that other techniques may be employed including rotationalengagement having a more complex or varied rotational or curvilinearpath controlled by a number of interconnected parts, as well as asliding engagement, such as along posts, that accommodates straight,linear engagement and disengagement of the opposing mounting surfaces1308, 1328 and any workpieces attached thereto.

The mounting surfaces 1308, 1328 may include a raised surface with aregular geometry or reference grid such as a regular pattern ofhexagons, circles, triangles, squares, or the like. A regular geometrywith centers spaced at a pitch of, e.g., 2 mm, or in other embodiments,between about 1 mm and 5 mm, or more generally, between 0.5 mm and 10mm, may provide significant advantages. Unlike the dental objectsattached thereto (which are typically specific to a dental patient), thearticulator 1300 may be mass produced with very high accuracy. Theinjection molded parts may be further refined with computerized millingor the like to improve local and global accuracy of the reference gridrelative to an electronic model thereof. The resulting mounting surfaces1308, 1328 may provide accuracy on the order of 25 microns for centerplacement of a repeating geometry. Thus, each hexagon (or circle,square, etc.) may be accurately centered.

By contrast, the corresponding dental objects (not shown) may beproduced using a process with, e.g., pliable materials or an unavoidabledegree of, for example, curing or thermal deformation that may affectoverall geometry. The use of a highly accurate reference grid forplacement of objects that repeats within a small range (e.g., less than2 mm) ensures localized accuracy for objects attached to the grid. Thatis, when the corresponding grid is applied to a digital model and aphysical object is fabricated from the digital model, dimensionalaccuracy of the physical object can be confirmed (in at least twodimensions) by mating the object to a known, accurate reference grid. Byembedding this reference grid into the articulator 1300, a localizedaccuracy check is implicitly performed each time an object is attachedto the grid. It will be understood that, while a repeating, hexagonalreference grid is depicted in FIG. 13 et seq., any number of variationsmay be employed including regular and irregular spacing (which may alsoregister each object in a unique location on the grid), and a variety ofrepeating or non-repeating shapes. Thus, in general, terms such as grid,regular grid, regular geometry, alignment grid, reference grid, and thelike will be understood to refer to any geometric pattern that can beimposed on an articulator in a mass production process with sufficientaccuracy to ensure localized accuracy of objects mated thereto. Whereirregular patterns, such as random patterns or varying shapes, areemployed, it will be understood that a relevant characteristic may befeature size rather than center spacing. Thus, individual shapes may beused within a pattern that has relatively large center spacing,relatively small center spacing, or varying center spacing, providedfeatures of the shapes within the reference grid provide features thatlocally verify accuracy of a corresponding model. The features mayinclude holes, arcs, angles, spurs, or any combination of these, or anyother suitable geometric pattern or patterns. The spacing of thesefeatures may be any distance suitable for the desired localization ofaccuracy, such as 2 mm, 3 mm, between about 1 mm and 5 mm, or moregenerally, between 0.5 mm and 10 mm, and each shape may include one ormore features.

In other embodiments, similar alignment grids may be applied along otherplane surfaces of fabricated dental objects, provided they do notinterfere with the creation of final dental works, such as along sidesor other handling surfaces thereof. These may serve as additionaldimensional checks even where they are not used for alignment of variouspieces in an articulator or the like.

It will also be understood that additional advantages may accrue fromsuch an alignment grid. By using a significant number of matingsurfaces, a good tension or friction fit may be maintained between thearticulator 1300 and pieces attached thereto. This may simplify handlingof workpieces by mitigating or removing the need for additionalfasteners and the like. Further, by distributing this fit along theentire mating surface, or a significant portion thereof, lateralstability of the inserted pieces may be increased for improved handlingof the assembled model. Further, the articulator 1300 may be fabricatedin a material such as polyphenylsulfone (“PPSF”) that providessufficient hardness and thermal resistance to be washed and reusednumerous times.

FIG. 14 shows a digital dental model with two partial arches inocclusion. The model 1400 may include two opposing surfaces such as apartial upper arch 1402 and a partial lower arch 1404 with at least onetooth surface 1404 prepared for an artificial dental object. It will beunderstood that the depiction of FIG. 14 is an example only. While thefigure depicts a partial upper and lower arch with a single toothprepared for a crown, the digital dental model may include more or lessof each opposing arch, and may include a tooth surface prepared for anyone or more dental objects suitable for fabrication using the techniquesdescribed herein. The opposing surfaces 1402, 1404 may be virtuallyaligned using, for example digital bite registration, such as byregistering the digital objects to a surface scan that spans both archeswhile the arches are in occlusion, as generally described above.

It will be understood that, while a partial arch model including aprepared tooth surface is depicted in this and the following figures,the techniques described herein may also, or instead, be suitablyapplied to models with or without prepared tooth surfaces, single toothmodels, quads, partial arches, full arches, and so forth.

FIG. 15 depicts a cross section of an alignment geometry including aregular geometry and a positioning key. As discussed above, thealignment geometry may include a regular geometry 1500 of hexagons 1502or other shapes, along with a positioning key 1504 or other mechanicalregistration feature adapted for unique positioning of one or moredental objects in a plane. In general, the positioning key 1504mechanically encodes positional information and the regular geometry1500 enforces local accuracy against a fixed reference array asdescribed above. The regular geometry 1500 and/or positioning key 1504may be embedded in raised and/or recessed surfaces of mating componentssuch as dental articulators (or bases, and so forth) and components ofdental models to capture relative position and orientation of thecomponents.

It will be understood that, while the positioning key 1504 is depictedas an orthogonal line pair, and such a key may be usefully employed withthe systems and methods described herein, a variety of other keys andregistration schemes may be usefully employed to uniquely positionobjects in an x-y plane of a mounting surface. Any such technique thatwould be apparent to one of skill in the art may be employed with thesystems described herein, provide it offers suitable scale and detailfor the dental models described herein.

When constructing an articulator such as the articulator 1300 describedabove for use with objects containing the alignment geometry, a numberof features may be included to improve ease of use and assembly. Forexample, the surface on the articulator corresponding to the positioningkey 1504 may be raised slightly (e.g., 0.1 mm, 0.5 mm, 1 mm, 2 mm, orany distance between these distances, or any other distance) to providetactile feedback during assembly. As another example, a single circularelement may extend substantially above the surface of the articulator(or above the mating surface of the dental object) as an alignment post,with a corresponding hole in the mating surface. This permits convenientcentering of an object by a user during assembly with both visual andtactile feedback. Once centered on the alignment post, further assemblyrequires only rotational alignment to the alignment geometry and anyassociated positioning keys. As another example, the opposing surfacesof the articulator and dental object(s) may be provided with athree-dimensional contour (such as a rectangular pyramid) that urges theopposing pieces into alignment during assembly. That is by providing acone or pyramid shape on one side, and an inverted duplicate of same onthe other, the two pieces will tend to move into alignment as they arepressed together, providing gross tactile feedback on proper alignment.

FIG. 16 shows a virtual application of an articulator geometry to adental model. In this digital model 1600, an alignment geometry 1602such as any of the alignment geometries described above, may bepositioned in two separated, parallel planes corresponding to theoperative positions of two halves of a dental articulator having thesame geometry. A dental model, which may include an upper surface 1604and a lower surface 1606 in occlusion as described generally above, maybe positioned within the planes of the alignment geometry 1602, eithermanually or automatically (e.g., by alignment relative to top and bottomplanes of the dental model).

The dental model may then be extended (again, either automatically ormanually) to intersect the planes of the alignment geometry 1602. Athree-dimensional model of the alignment geometry 1602 may then be addedto the digital model that mechanically corresponds to the alignmentgeometry of an articulator, such as any of the articulators describedabove. Where the planes of the alignment geometry 1602 representinnermost bounds of the articulator surfaces, the dental model may thenbe further extended or extruded to a length corresponding to anoutermost bound of the articulator. Where the planes of the alignmentgeometry 1602 represent outermost bounds of the articulator surfaces,the alignment geometry may be projected inward on the surfaces of thedental model (using, e.g., an exclusive or (“XOR”) or other operation)to a depth reaching to the innermost bounds of the articulator surfaces.The resulting digital model 1600 is prefit and prealigned to a dentalarticulator having corresponding alignment geometry and positioningkeys.

It will be understood that, while the articulator described aboveemploys two plane surfaces that are parallel when arches of the modelare occluded, this is not strictly required, and any alignment orpositioning may be employed that suitably presents occlusion andalignment data to a technician who is fabricating a dental objecttherefrom. It will also be understood that additional process may berequired as will be readily appreciated by one of ordinary skill in theart. For example, the side walls of a PPSF injection molded part mayrequire a pitch of 1° to insure that the part can be removed from amold. A corresponding pitch may be added to the three-dimensionalalignment geometry of the digital model 1600 for a good fit. Inaddition, tolerances may be varied to increase or decrease the tightnessof fit between assembled parts, which may be specified on a part bypart, customer by customer, or global basis. In another aspect, theshape of the mating three-dimensional surface of the model need notcorrespond to the shape of the dental model. That is, the mating surfaceof the dental model may be digitally fashioned as a base plate largerthan the cross-section of the dental object, or as a regular geometrysmall than the dental model, such as a square or rectangle fit withinthe cross-sectional bounds of the dental model, or some other shapeindependent of the cross-sectional shape of the dental model. All suchvariations are intended to fall within the scope of this disclosure.

FIG. 17 shows a dental model including alignment geometry. An upper arch1701 and a lower arch 1702 generally present features such as a regulargeometric array and positioning keys that will mechanically register aphysical model fabricated therefrom in correct orientation within adental articulator such as the articulator 1300 described above. It willbe noted that the digital dental model 1700 may be further processedprior to fabrication as described generally above. For example, inconventional dentistry, dies are manually cut from a dental model by adental technician for preparation of a restoration. However, applyingthe principles described herein, a die 1708 may be virtually cut from afirst and second adjacent regions 1704, 1706 of the lower arch 1702during a modeling step (as described generally above). Each portion ofthe model may be separately manufactured, which permits, for examplemanufacture of the die 1708 from a different material and/or using adifferent process, as described for example with reference to FIG. 9above. Thus the die 1708 may be milled from a ceramic while the otherregions 1704, 1706 may be fabricated using DLP, stereo-lithography, orthree-dimensional printing. For computerized milling or the like, abillet may be preformed with the regular geometry and/or positioning keyintegrated therein. This may provide an additional advantage oforienting the workpiece in the milling environment, such as through useof a support device with a surface corresponding to the surface(s) of anarticulator. Thus in one embodiment, a technique for fabricating pre-cutdental models directly from a digital model is disclosed.

Other modeling techniques described above may also be employed to assistin transitioning from a digital dental model to a physical dental model,such as the virtual die spacing, occlusal relief, ditching of the die,and so forth.

FIG. 18 shows pieces of a dental model fabricated from a digital dentalmodel. FIG. 18A shows a first portion of a lower arch corresponding to afirst adjacent region 1706 of a lower arch 1702 in FIG. 17 above. FIG.18B shows a cut die corresponding to the die 1708 of FIG. 17 above. FIG.18C shows a second portion of a lower arch corresponding to the secondadjacent region 1704 of FIG. 17 above. FIG. 18D shows an upper archcorresponding to the upper arch 1701 of FIG. 17 above.

It will be understood that the pieces of a dental model illustrated inFIGS. 18A-18D may be fabricated in a number of ways. For example theymay be fabricated as a kit using, e.g., stereo-lithography or digitallight processing as described above, and may include an interconnectingwire frame or other structure to keep the pieces joined together untilthey reach a dental technician or other handler. They may be fabricatedfrom different materials or using different processes as describedgenerally above. They may include bar codes, embedded radio-frequencyidentification (“RFID”) tags, color coding, or other markings oridentification technologies to assist in tracking and handling largenumbers of parts.

FIG. 19 shows a dental model assembled on an articulator. In general,the assembled model may include a first section 1902 and a secondsection 1904 of an articulator, a first arch 1906 (or partial arch), anda second arch precut into a first piece 1908, a second piece 1910, and athird piece 1912 for use in fabrication of an artificial dental objectsuch as a crown, prosthesis, and the like. A regular geometric arrayand/or positioning keys molded into the sections 1902, 1904 of thearticulator may physically mate with corresponding surfaces of the modelpieces 1906, 1908, 1910, 1912 to providing an articulating model thatreproduces the orientation of dental structures from a dental patient.The assembled model may capture various aspects of static articulationsuch as occlusal contact points and arch positions in various types ofocclusion, as well as dynamic occlusion such as lateral excursions, jawmotion, and the like.

It will be appreciated that, the mechanical registration features 802may also, or instead, be used to orient a single die (not shown), or anumber of dies within a dental model. In one embodiment, an entire archmay be precut and pre-indexed within a virtual environment in themodeling step(s) described above, using varying degrees of automation.

FIG. 20 shows another embodiment of a dental articulator. Thearticulator 2000 may include a first arm 2002 and a second arm 2004,such as the arms described above. Each arm 2002, 2004 may include amounting surface 2006 with a reference grid surrounded by a retainingwall 2007 that includes a positioning key comprised of a number ofalignment guides 2008. Each arm 2002, 2004 may also include visualmarkings 2010 such as letters or other markings to assist a user inassembling components of a model on the arms 2002, 2004. It will beunderstood that while visual markings 2010, the retaining wall 2007, thealignment guides 2008, and the regular geometry of the mounting surface2006 are illustrated only for the first arm 2002, that some or all ofthese features may also, or instead, be on the opposing second arm 2004even though they are not visible in the perspective drawing of FIG. 20.

The retaining wall 2007 may provide lateral stability to object insertedinto the articulator 2000, or may enhance stability provided by thereference grid as described above. The alignment guides 2008 may providea positioning key to support unique positioning of separate componentswithin a dental (or other) model. Thus, for example, as depicted in FIG.20, the alignment guides 2008 may have a gradually increasing width fromguide to guide along the retaining wall 2007 in order to providemechanical registration for a number of pieces. Similarly, variations inspacing, shape, and size may be employed to mechanically register modelcomponents within the space defined by the retaining wall 2007. Inaddition to this mechanical registration, the visual markings 2010,which may be letters, numbers, symbols, or the like, may provide visualindicators of object positioning that are correlated to similar oridentical visual markings printed on model components. In this manner, auser assembling objects to the articulator 2000 is provided with visualindicators of position, reinforced with mechanical registration of thealignment guides 2008.

It will also be appreciated that the embodiments described above are byway of example and not limitation. Dental models fabricating using thetechniques described herein may include, without limitation, apre-manufactured base upon which dental models are aligned. Moregenerally, the fabrication technologies described above may be used incombination with a variety of digital modeling tools to directlyfabricate dental objects such as restorations, prosthetics, appliances,and hardware, as well as a variety of interim components of dentalmanufacture used to create any of the foregoing. The dental model, orportions thereof, may be directly printed from the digital model as aplurality of preindexed components ready for assembly at a dentallaboratory.

Leveraging rapid fabrication technologies such as milling and stereolithography allows for the virtual creation and direct fabrication ofthe individual components of a precut, preindexed, and/or prearticulateddental model such as described above with reference to FIGS. 13-20. Thusin one embodiment, disclosed herein is a method and system forfabricating a dental model including a plurality of components. Whilethis may include the components of a dental model described above, itmay also, or instead, include other components such as investment molds,waxups, and so forth, which may be modeled with varying degrees ofautomation and transmitted to a dental laboratory or rapid manufactureras a virtual model of a kit of cooperating dental components. Some orall of the components of the kit may then be directly fabricated fromthe virtual model.

Thus there is disclosed herein direct fabrication of restorations andappliances from digital models such as digital surface representationsacquired from human dentition. This fabrication, and any of the otherfabrication processes described herein may be performed, for example, ata dental laboratory or at an in-office dental laboratory at a dentist'soffice.

While the invention has been disclosed in connection with certainpreferred embodiments, other embodiments will be recognized by those ofordinary skill in the art, and all such variations, modifications, andsubstitutions are intended to fall within the scope of this disclosure.Thus, the invention is to be understood with reference to the followingclaims, which are to be interpreted in the broadest sense allowable bylaw.

1. A computer program product comprising computer executable code that,when executing on one or more computing devices, performs the steps of:aligning a first digital dental model of at least a portion of an upperarch with a second digital dental model of at least a portion of a lowerarch using a digital bite registration to obtain an occluded model;extending the occluded model to meet a digital three-dimensional modelof a dental articulator at two mounting surfaces thereof, each mountingsurface including a raised surface with a reference grid and apositioning key to provide a mechanically registered digital dentalmodel; and converting the digital dental model into a form suitable forfabrication.